在没有 JLabel 的 Swing 中显示文本[关闭]

Question

我必须使用 Swing 制作一个 Java 程序，我想显示一些文本，但不使用 JLabel（包括文本组件）！我必须扩展JFrame。我还有什么其他选择？

Answer 1

你不应该：

• 不必要地扩展JFrame
• 通过paint(..)直接绘制到JFrame

你应该：

• 覆盖JComponents paintComponent(...)
• 在paintComponent(...)做自定义绘画，
• 将JComponent 实例添加到JFrame

这里有一个例子：

import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;

public class DrawSimpleText {

    public DrawSimpleText() {
        initComponents();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new DrawSimpleText();
            }
        });
    }

    private void initComponents() {
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.getContentPane().add(new JPanel(true) {
            Font font = new Font("Serif", Font.PLAIN, 20);
            String s = "Java Source and Support";

            @Override
            public void paintComponent(Graphics g) {
                super.paintComponent(g);
                Graphics2D g2 = (Graphics2D) g;

                g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                        RenderingHints.VALUE_ANTIALIAS_ON);
                g2.setFont(font);

                FontMetrics fm = g.getFontMetrics(font);

                int width = fm.stringWidth(s);

                Dimension d = getSize();

                //center String/text
                int cx = (d.width - width) / 2;
                int cy = (d.height - fm.getHeight()) / 2 + fm.getAscent();

                g2.drawString(s, cx, cy);
            }

            @Override
            public Dimension getPreferredSize() {
                return new Dimension(300, 100);
            }
        });
        f.pack();
        f.setVisible(true);
    }
}

更新：

根据您的评论 尽管它违反了所有 Swing 规则和我自己的道德：

但是，如果您仍然需要这样做（我无法理解为什么这是不好的做法），方法如下：

import java.awt.Dimension;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import javax.swing.JFrame;
import javax.swing.SwingUtilities;

public class DrawSimpleText extends JFrame {

    public DrawSimpleText() {
        initComponents();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new DrawSimpleText();
            }
        });
    }

    private void initComponents() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        pack();
        setVisible(true);
    }
    Font font = new Font("Serif", Font.PLAIN, 20);
    String s = "Java Source and Support";

    @Override
    public void paint(Graphics g) {

        super.paint(g);
        Graphics2D g2 = (Graphics2D) g;

        g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON);
        g2.setFont(font);

        FontMetrics fm = g.getFontMetrics(font);

        int width = fm.stringWidth(s);

        Dimension d = getSize();

        //center String/text
        int cx = (d.width - width) / 2;
        int cy = (d.height - fm.getHeight()) / 2 + fm.getAscent();

        g2.drawString(s, cx, cy);
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(300, 100);
    }
}